Here's another hard case, looks wide enough to hold a laptop.
http://www.bikemania.biz/Cargo_Cache...cargocache.htm

For groceries, if they won't fit in there, a grocery pannier like this one is pretty handy:
http://www.bikemania.biz/Bike_Pro_US...basket-c12.htm

They fold flat or unhook from your rack for storage. Like mentioned above, you should be able to adjust a rack back away from your big ol feet.